What Von said is true, but I also think it depends on what style of fighter you are. If you are a pressure/Insider fighter who like throw Left Hooks to the head and body and Uppercuts, bobbing and weaving is ideal (or as you put it "rolling".

If you throw the Left Hook and your opponent throws a Cross, Bob and weave to your left underneath the Cross. This is if you're an Inside fighter type.

However, if you're more like an Outside Fighter type, like the style I used to spar in, you'll move in with the Left Hook, and side step to the right after throwing it to avoid getting hit by the Cross. No need for unnecessary bobbing and weaving, especially if you're a taller guy.

That's my advice.